1. Field of the Invention
The present invention relates to an IC card. In particular, it relates to a structure of IC cards such as CFast that connect to a slot installed on a computer.
2. Related Art
For example, in order to expand functionality of a personal computer (hereinafter, referred to as a “PC”), an expansion card, in which a connector is added to a printed circuit board that has been equipped with a microcomputer, is connected to an expansion slot of a PC. The CFast card is one type of expansion card standardized for a PC, and connects to a PC, achieving high speed communication.
Although the CFast card is one type of IC card, a printed circuit board equipped with a microcomputer is housed in a rigid body frame thereof. Accordingly, the CFast card can be classified as a different microcomputer card from a memory card in which a memory chip is sealed within a plastic package. Furthermore, in recent years, a CFast card equipped with a keyboard has appeared, and CFast cards can also be classified as multifunction cards.
Such IC cards have a printed circuit board disposed on an interior portion of a rectangular flat frame. The frame has a connector electrically connected to the printed circuit board, and both sides of the connector and the frame are covered by a metal plate shell, thereby constituting a rigid outer shell.
An IC card having such a structure is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2002-279388 (hereinafter called “Patent Document 1”). Patent Document 1 discloses an IC card and manufacturing method thereof in which irregularities in bonding strength between a metal plate shell and a synthetic resin frame are eliminated, resulting in having a more stable and robust bonding force, and allowing for a reduction in a manufacturing cost.
The IC card according to Patent Document 1 has a printed circuit board including an electronic component in an interior portion thereof, and is formed by covering a synthetic resin frame with a metal plate shell. Then, the frame forms a groove for fitting the shell on a side bordered by the shell. Furthermore, on the shell is established a protruding portion which is inserted into the groove. The protruding portion is shaped such that a front end section is wider than a base section. In addition, the groove of the frame and the protruding portion established on the end face of the shell are joined by ultrasonic welding (pressure welding).
The IC card according to Patent Document 1 is such that the metal plate shell is composed of stainless steel, and a plate thickness is 0.1 mm to 0.2 mm. Furthermore, the IC card according to Patent Document 1 is such that, if a groove portion of a frame on a protruding portion is subjected to pressure and vibrated with ultrasonic waves, then a portion of a synthetic resin frame hardens after welding, allowing the protruding portion to be joined.
However, the IC card according to Patent Document 1 is such that, although welded synthetic resin flows into a base portion of the protruding portion, the plate thickness of the protruding portion is so thin that the protruding portion easily peels off from the frame. It is believed that when a force to separate from the frame acts upon the shell, the protruding portion destroys the welded portion of the frame in a manner similar to a thin blade slicing the frame, and there is a problem in that a joining strength between the shell and the frame is insufficient.